1. Field
The field of the invention is towing systems for snow grooming devices propelled behind tracked vehicles, and more particularly, such devices having provisions for corrective adjustment of longitudinal alignment with the towing vehicle.
2. State of the Art
Initial attempts to secure snow grooming devices to towing vehicles probably employed simple vertical pivot mechanisms after the manner of highway trailer hitches. Shortcomings of this approach for use upon the steep terrain of ski slopes soon dictated the development and use of more sophisticated towing arrangements. Operating across hillsides, for example, caused the implement to swing sharply downhill about the connecting pivot. Similarly, when a path is groomed directly down a slope along the fall line, the towing vehicle often must restrain the free downward progress of the groomer, causing one side or the other of the implement to cock sidewise of the path. It is only with very rare directly uphill grooming paths that such towing problems would not occur.
Improvements in snow grooming equipment towing have been incorporated into a device known in the trade as an "articulated lift frame", which spans between the implement and the towing vehicle. The front end of this frame is pivotally joined to the towing vehicle along a laterally directed horizontal axis. A tow beam or bar is joined to the front end portion through a vertical pivot, and is rigidly secured at its rearmost end to the grooming implement. Hydraulic ram and cylinder assemblies, horizontally spaced apart, act between the frame front end and the tow beam to adjust alignment of the grooming implement.
Flow of hydraulic fluid to the cylinders is controlled by manually controlled electric valves, which are then manually commanded to the closed position after the alignment is corrected to the operator's visual satisfaction. The effectiveness of this arrangement is heavily dependent upon the skill and alertness of the operator, who also must control and direct the towing vehicle. The alignment is accomplished through backwardly viewing the device from the operator's seat during forward operation of the vehicle. Often, it is necessary to stop the vehicle for necessary alignment adjustment before continuation of a grooming path. Further, since the cylinders must be placed in float condition during sharp turns, adjustment is necessary at the beginning of each grooming pass.
The towing vehicle is provided also with a cylinder and ram connected to rotate the lift frame about the horizontal pivot axis to an upward, carrying position. The operator must align the frame during this process, to raise the implement into proper laterally horizontal carrying position.
Clearly, improvement in snow groomer towing apparatus is needed beyond the visually and manually adjusted state of the art towing frames presently available.